Optical recording method and optical recording device

ABSTRACT

In a dye-type optical recording medium, a write strategy for use in recording is determined based on recommended write strategy parameters recorded on an optical disk ( 160 ) and the characteristics of the optical recording device, and recording is carried out on the optical disk ( 160 ) according to the determined write strategy. In a medium of the phase change type, a power ratio and modulation degree for use in recording are determined from a recommended pulse width value in the recommended write strategy parameters recorded in the optical disk ( 160 ), the recommended power ratio value, the recommended recording power value, and the characteristics of the optical recording device, and recording is carried out on the optical disk ( 160 ) according to the power ratio value and modulation degree value thus determined. Optimal recording can be carried out even on an optical disk for which the optimal write strategy information has not been determined in advance, without the need to store write strategy information suitable for each and every optical disk.

This application is a Divisional of co-pending application Ser. No.11/587,697, filed on Oct. 26, 2006, the entire contents of which arehereby incorporated by reference and for which priority is claimed under35 U.S.C. §120.

FIELD OF THE INVENTION

The present invention relates to an optical recording method and anoptical recording device for recording information on an opticalrecording medium, more particularly to a method of determining the writestrategy to use in recording.

BACKGROUND ART

One example of a conventional optical recording device is a devicehaving a recording and reproducing unit with a strategy section thatcontrols the write strategy for writing to an optical disk, and astrategy information recording unit in which strategy information foroperating the strategy section is recorded; strategy informationcorresponding to device information about the recording device andmedium information about the optical disk is recorded in the strategyinformation recording section, read from the strategy informationrecording section, and transferred together with the medium informationto the recording device. Default strategy information is also recordedin the strategy recording section in this device; if strategyinformation corresponding to the device information and mediuminformation transferred from the recording device is not recorded on thestorage information recording section, the default strategy informationis read and transferred to the recording device (see, for example,Patent Document 1).

Patent Document 1: Japanese Patent Application Publication No.2002-56531 (pp. 1-9, FIGS. 1-15)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the above conventional optical recording device, as it is necessaryto first investigate and then store in the optical recording device alarge amount of strategy information corresponding to device informationand medium information, much labor was required, and many storagedevices such as memory devices were needed. Another problem has beenthat, since default strategy information is used when strategyinformation corresponding to the device information and mediuminformation is not stored in the recording device, there are recordingmedia that cannot be recorded on correctly because of mismatchingrecording conditions, depending on the optical conditions of the opticaldisk and the optical pickup.

The present invention addresses the above problems, a first object beingto obtain an optical recording method and optical recording device thatdo not require the storage of all strategy information suitable forevery optical disk and thus do not require storage devices of largecapacity.

A second object is to obtain an optical recording method and opticalrecording device with which appropriate recording can be carried outeven on an optical disk for which the optimal strategy information hasnot been determined in advance.

Means of Solution of the Problems

The present invention provides an optical recording method comprisingthe steps of:

-   -   reading recommended write strategy parameters from a dye-type        optical recording medium on which the recommended write strategy        parameters have been recorded;    -   determining the pulse widths of a write strategy for recording        each mark, based on the recommended values of the leading pulse        width and multi-pulse width in the write strategy for recording        the shortest mark included in the recommended write strategy        parameters that were read and characteristics of the optical        system of the optical pickup of the optical recording device        used in recording; and    -   writing to the optical recording medium by use of the optical        recording device, using the write strategy thus determined.

Effect of the Invention

According to the present invention, given the recommended write strategyparameters recorded on the optical recording medium, an appropriatewrite strategy responsive to the characteristics of the optical systemof the optical pickup of the optical recording device used in recordingcan be determined, and recording can be carried out using the optimalwrite strategy.

A further effect is that it is not necessary to determine theappropriate write strategy for all optical recording mediaexperimentally beforehand, so labor and cost can be saved, and alarge-capacity memory is not required.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an optical recording device in a firstembodiment of this invention.

FIGS. 2( a) to 2(c) shows examples of asymmetry values of the reproducedsignal detected in the asymmetry detector in the first embodiment ofthis invention.

FIG. 3 shows examples of write strategies generated in the opticalrecording device in the first embodiment of this invention when theoptical disk is a medium of the dye type.

FIG. 4 is a flowchart illustrating the recording procedure in theoptical recording device in a first embodiment of this invention.

FIG. 5 is a flowchart for calculating the write strategy fromrecommended write strategy parameters recorded on an optical disk in theoptical recording device in the first embodiment of this invention.

FIG. 6 illustrates the relationship between a pulse width 2TF and arecommended write strategy parameter 2TP in the optical recording devicein the first embodiment of this invention.

FIG. 7 illustrates the relationship between a pulse width LTF and arecommended write strategy parameter LTP in the optical recording devicein the first embodiment of this invention.

FIG. 8 illustrates the relationship between pulse widths 1TF and 2TF inthe write strategy in the optical recording device in the firstembodiment of this invention.

FIG. 9 illustrates the relationship between pulse widths LTF and 3TF inthe write strategy in the optical recording device in the firstembodiment of this invention.

FIG. 10 illustrates the relationship between the pulse width TM and therecommended write strategy value TMP×2TP×LTP/1TP in the opticalrecording device in the first embodiment.

FIG. 11 illustrates the relationship between an asymmetry value β1recorded on the optical disk and an asymmetry value β2 used in recordingin the first embodiment of this invention.

FIG. 12 illustrates the relationship between jitter value and the writestrategy used in recording in the optical recording device in the firstembodiment of this invention.

FIG. 13 is a block diagram showing an optical recording device in asecond embodiment of this invention.

FIGS. 14( a) and 14(b) shows examples of modulation degrees of thereproduced signal detected in the modulation degree detector in thesecond embodiment of this invention.

FIG. 15 shows examples of write strategies generated in the opticalrecording device in second and third embodiments of this invention whenthe optical disk is a medium of the phase change type.

FIG. 16 is a flowchart illustrating the recording procedure in theoptical recording device in the second and third embodiments of thisinvention.

FIG. 17 illustrates the relationship between the recommended writestrategy value PW1×εP1×TMP1 and the power ratio ε1 in the opticalrecording device in the second embodiment of this invention.

FIG. 18 illustrates the relationship between the recommended writestrategy value TMP1×TCP1/1TP1 and the modulation degree MOD1 used forrecording in the optical recording device in the second embodiment.

FIG. 19 illustrates the relationship between jitter value and the powerratio used in recording in the optical recording device in the secondembodiment of this invention.

FIG. 20 illustrates the relationship between the recommended recordingcondition value (PW2̂2×εP2)/1TP1 recorded on the optical disk and thepower ratio ε2 in the optical recording device in the third embodiment.

FIG. 21 illustrates the relationship between the recommended recordingcondition value 1TP2×PW2 recorded on the optical disk and the modulationdegree MOD2 used in recording in the optical recording device in thethird embodiment of this invention.

FIG. 22 illustrates the relationship between jitter value and the powerratio used in recording in the optical recording device in the thirdembodiment of this invention.

EXPLANATION OF REFERENCE CHARACTERS

100 optical recording device, 110 semiconductor laser, 120 laser driver,130 collimator lens, 140 beam splitter, 150 objective lens, 160 opticaldisk, 170 sensor lens, 180 photodetector, 190 head amplifier, 200 datadecoder, 210 pre-pit detector, 220 asymmetry detector, 230 data encoder,240 laser waveform controller, 250 central controller, 260 modulationdegree detector

BEST MODE OF PRACTICING THE INVENTION

The recording method and recording device in the present inventionrecord information on an optical disk on which recommended writestrategy parameters or recommended recording conditions have beenprerecorded. The recommended write strategy parameters or recommendedrecording conditions represent a write strategy or recommended recordingconditions suitable for use in recording on the optical disk, and arerecorded in the form of pre-pits, for example, in a predetermined areaon the optical disk: the lead-in area, for example.

The optical disk includes, for example, a groove part (not shown)comprising grooves in which information is recorded, and a land part(not shown) between the grooves; the recommended write strategyparameters (including the recommended recording power) set by therecording media manufacturer are recorded in the land part together withother information such as an asymmetry value.

The recommended write strategy parameters envision that that recordingwill be performed under predefined conditions. For different recordingconditions, therefore, it is preferable to use a write strategydifferent from the recommended write strategy parameters. According tothe present invention, a write strategy is determined based on therecommended write strategy parameters or recommended recordingconditions read from the optical disk, and on the characteristics of theoptical system of the optical pickup of the optical recording deviceused in recording, and recording is performed by use of the writestrategy thus determined.

First Embodiment

Embodiments of the invention will now be described with reference to theattached drawings.

The optical recording method in the embodiments below performs mark-edgerecording (PWM recording). To record information, it causes asemiconductor laser to emit multiple pulses to form recording marks,based on the data to be recorded on the optical disk. In other words,the write strategy used in the following embodiments is a strategy ofthe multi-pulse type, having one or more pulses in the mark period. Inthe embodiments described below, in a write pulse strategy of thismulti-pulse type, the pulse widths are changed responsive to thecharacteristics of the optical system of the optical pickup of theoptical recording device.

In addition, in the embodiments described below, the recording ofinformation onto the optical disk is carried out by illuminating theoptical disk with optical pulses in patterns corresponding to the 3T to11T and 14T marks (T being the channel clock period) in EFM modulation.

The longest mark (the mark with length 14T) is a sync pattern.

FIG. 1 shows an example of the basic structure of an optical recordingdevice 100 according to the first embodiment of the invention. In FIG.1, the semiconductor laser 110 used as a laser light source is drivenand controlled by a laser driver 120.

When data are reproduced, a laser beam emitted from the semiconductorlaser 110 with the output value (reproducing power) necessary for datareproduction is focused onto the optical disk 160 through a collimatorlens 130, beam splitter 140, and objective lens 150. The light reflectedfrom the optical disk 160 passes through the objective lens 150, isseparated from the incident light by the beam splitter 140, and is thenreceived through a sensor lens 170 by a photodetector 180.

In the above structure, the semiconductor laser 110, collimator lens130, beam splitter 140, objective lens 150, and sensor lens 170constitute the optical system, which in turn, together with thephotodetector 180, constitutes the optical pickup.

The photodetector 180 converts the optical signal to an electric signal.The electric signal converted by the photodetector 180 is input througha head amplifier 190 into a data decoder 200, a pre-pit detector 210,and an asymmetry detector 220. The data decoder 200 generates(reproduces) the data recorded on the optical disk 160 by performingsuch processes as demodulation and error correction on the inputelectric signal.

From the input electric signal, the pre-pit detector 210 detects pre-pitinformation including such information as the recommended write strategyparameters, which are the recommended parameters of the write strategyto be used for recording on the optical disk 160.

The asymmetry detector 220 couples the input electrical signal by AC(alternating current) coupling and detects the peak level A1 and bottomlevel A2 of the AC-coupled electrical signal. Using the equation (1)below, it calculates an asymmetry value β from the detected peak levelA1 and bottom level A2.

β=(A1+A2)/(A1−A2)   (1)

The peak level A1 and bottom level A2 occur in places where spaces ofmaximum length alternate with marks of maximum length; these values areexpressed with a zero level equal to the average value of the peak leveland bottom level in places where spaces of minimum length and marks ofminimum length appear alternately.

FIGS. 2( a) to (c) show examples of the detection of the asymmetry valuein the detected reproduced signal in the asymmetry detector 220. FIG. 2(a) illustrates the case in which β<0. FIG. 2( b) illustrates the case inwhich β=0. FIG. 2( c) illustrates the case in which β>0.

In the recording of data, a data encoder 230 adds error correctionsymbols to the original data to be recorded and modulates the data togenerate the recording data on which the driving signal to thesemiconductor laser 110 is based. A laser waveform controller 240generates a write strategy signal based on the recording data. Whenprovided with recording data specifying one of 3T to 11T or 14T by acentral controller 250, that is, the laser waveform controller 240outputs a write strategy signal corresponding to the provided recordingdata (a signal having a waveform approximately matching the waveform ofthe emitted optical pulse train).

The laser driver 120 drives the semiconductor laser 110 with drivingcurrent responsive to the write strategy signal thus generated. A laserbeam emitted from the semiconductor laser 110 with the output value(recording power) necessary for recording the data is focused onto theoptical disk 160 through the collimator lens 130, beam splitter 140, andobjective lens 150. The information is thereby recorded.

FIG. 3 shows an example of a write strategy generated in the laserwaveform controller 240 in the optical recording and reproducingapparatus 100 shown in FIG. 1 when the optical disk 160 is a medium ofthe dye type. FIG.(a) shows a channel clock having a period T. FIG. 3(b) shows recording data comprising marks and spaces. FIG. 3( c) showsthe write strategy, i.e., the emitted optical pulse pattern, forrecording the data in FIG. 3( b). In the emitted optical pulse pattern,the level is changed between the recording power level and reproducingpower level, and the width of each pulse is defined as the period spentat the recording power level.

The shortest mark has a length corresponding to 3T, while the longestmark has a length corresponding to 14T.

FIG. 3( b) and FIG. 3( c) show a case in which the shortest mark isrecorded, then the fourth-shortest mark is recorded.

As shown at the left in FIG. 3( c), when the recorded data are theshortest mark, the write strategy consists only of a leading pulse Fhaving pulse width 1TF.

As shown at the right in FIG. 3( c), the write strategy for recordingthe fourth shortest mark consists of a leading pulse F having pulsewidth LTF followed by three multi-pulses M.

The write strategy for recording the n-th shortest mark (4<n<10, havinga length corresponding to ((n+2)T) consists of a leading pulse F havingpulse width LTF, followed by (n−1) multi-pulses M.

The write strategy for recording the longest mark (a mark having length14T) consists of a leading pulse F having pulse width LTF, followed byeleven multi-pulses M.

As shown, the marks from the fourth shortest mark to the longest markhave the same leading pulse width LTF.

The write strategy for recording the second shortest mark consists of aleading pulse F having pulse width 2TF, followed by one multi-pulse M.

The write strategy for recording the third shortest mark consists of aleading pulse having pulse width 3TF, followed by two multi-pulses M.

The width of the multi-pulses M is the same in all of the cases above.

During reproducing and writing operations by the semiconductor laser110, the central controller 250 controls the device as a whole. Thecentral controller 250 receives reproduced data from the data decoder200, pre-pit information from the pre-pit detector 210, and an asymmetryvalue from the asymmetry detector 220, and provides control signals tothe data encoder 230, the laser waveform controller 240, and the laserdriver 120.

In particular, the central controller 250 controls the determination ofthe write strategy, especially the calculation of pulse widths and theasymmetry value, and trial writing performed by use of a modified writestrategy and asymmetry value, as will be described later with referenceto FIGS. 4 and 5.

The central controller 250 comprises, for example, a central processingunit (CPU), a program memory such as a read-only memory (ROM), forexample, storing programs for the operation of the CPU, and a datamemory such as a random-access memory (RAM), for example, for storingdata. The program memory stores constants (Ki, Ci, etc.) for variouscalculations described later. The program stored in the program memoryspecifically includes a section defining equations for determining thewrite strategy and equations for determining the recording conditions,as described later with reference to FIGS. 4 and 5.

It is a general practice to optimize the recording power by performingtrial writing before recording information. The procedure will bedescribed below.

First, trial writing on the optical disk 160 is performed by use of atest pattern comprising 3T-11T spaces and marks corresponding to randomrecording data, for example, under varied recording power; next, thearea on the optical disk 160 on which this test pattern has beenrecorded is reproduced, the asymmetry value is detected by the asymmetrydetector 220, and the detected asymmetry value is compared with a targetasymmetry value in the central controller 250 to obtain the optimalrecording power.

In general, the higher the recording power, the higher the asymmetryvalue, and the lower the recording power, the lower the asymmetry value.

The central controller 250 compares the detected asymmetry valuescorresponding to a plurality of mutually differing recording powers withthe target asymmetry value, and sets the optimal recording power as therecording power that generated a detected value nearest to the targetvalue.

Alternatively, the trial writing on the optical disk 160 may beperformed at one recording power, the data may be reproduced, theasymmetry value may be detected from the reproduced data, the detectedasymmetry value may be compared with the target asymmetry value, and therecording power may be increased or decreased responsive to thecomparison result to find the optimal value.

Within this basic information recording method, in the presentinvention, the pulse widths in the write strategy used for recording andrecording conditions such as the target value for adjusting the optimalpower are obtained by calculations based on the recommended writestrategy parameters and recommended recording conditions recorded on theoptical disk 160 and the characteristics of the optical system of theoptical pickup of the optical recording device used in recording; thenthe calculated pulse widths and recording conditions are used inrecording.

Next, the procedure followed in the optical recording method of thisembodiment will be described with reference to FIG. 4.

First, when the optical disk to be used in recording is inserted in theoptical recording device, in step S11, the recommended write strategyand recording condition parameters, i.e., the recommended values iTP(i=1, 2, 3, L) of the leading pulse width in the write strategy forrecording each mark, the recommended value TMP of the multi-pulse widthin the write strategy, and the recommended asymmetry value β1 are read(step S11).

The recommended write strategy parameters include the recommended valueof the leading pulse width in the write strategy for recording eachmark. As the recommended values iTP of the leading pulse width, at leastthe following values are read:

-   -   a recommended pulse width 1TP of the leading pulse F for        recording the shortest mark;    -   a recommended pulse width 2TP of the leading pulse F for        recording the second shortest mark; and    -   a recommended pulse width LTP of the leading pulse F for        recording marks from the fourth shortest mark to the longest        mark.

The recommended asymmetry value β1 is the target value used to determinethe recording power in trial writing.

Next, in step S12, the write strategy to be used in recording isdetermined based on the recommended write strategy parameters that wereread and the characteristics of the optical system of the optical pickupof the optical recording device used in recording (step S12). Detailswill be given later.

Next, in step S13, the asymmetry value β2 to be used in recording iscalculated according to the following equation (2), based on thenumerical aperture NA1 used for determining the recommended writestrategy parameter and the recommended asymmetry value β1 that were readin step S11 as described above, and the numerical aperture NA2 of theobjective lens 150 of the optical recording device 100 used in recording(step S13).

β2=β1E×(NA2−NA1)   (2)

The numerical aperture NA1 is known; data representing the numericalaperture NA1 are prestored in a non-volatile memory (comprising ROM, forexample) in the central controller 250. Data representing the numericalaperture NA2 of the objective lens 150, and the constant E have alsobeen stored in the non-volatile memory in the central controller 250;these data are read and used for the calculation according to equation(2).

Next, when a recording command is received, trial writing on the opticalrecording medium is performed in step S14, using the write strategyparameters and asymmetry value obtained as above. That is, the writestrategy determined in step S12 is set in the laser waveform controller240, which in turn generates write strategies based on the test patternto perform trial writing to the optical disk 160. The asymmetry value β2obtained as above is used as a target value. That is, the optimalrecording power is determined by reproducing the area on the opticaldisk 160 on which the test pattern has been recorded, comparing theasymmetry value detected by the asymmetry detector 220 with theasymmetry value β2 calculated in step S13, and performing control tomake the two values match.

Then, after this trial writing has been performed and the power has beenadjusted, the adjusted recording power and the write strategy obtainedin step S12 are used in step S15 to record data. That is, the writestrategy determined in step S12 is set in the laser waveform controller240, which in turn, generates write strategies based on the recordingdata, and performs writing onto the optical disk 160 with the recordingpower determined in step S14

Once the write strategy determined in step S12 has been set in the laserwaveform controller 240 in FIG. 1, when the central controller 250specifies one of 3T to 11T or 14T, a write strategy signal correspondingto the specified value is output from laser waveform controller 240.

FIG. 5 shows the determination process in step S12 in FIG. 4 in moredetail.

In step S121, the pulse width 2TF of the leading pulse F for recordingthe second shortest mark is calculated from the recommended pulse width2TP obtained in step S11 and constants K2 and C2, by use of thefollowing equation (3).

2TF=K2×2TP+C2   (3)

In step S122, the pulse width LTF of the leading pulse F for recordingthe marks from the fourth shortest mark to the longest mark iscalculated from the recommended pulse width LTP obtained in step S11 andconstants KL and CL, by use of the following equation (4).

LTF=KL×LTP+CL   (4)

In step S123, the value of the pulse width 2TF calculated in step S121is set as the pulse width 1TF of the leading pulse F for recording theshortest mark.

The value of the pulse width LTF calculated in step S122 is set as thepulse width 3TF of the leading pulse F for recording the third shortestmark.

In step S124, the pulse width TM of the multi-pulses M is calculatedfrom the recommended pulse widths 1TP, 2TP, LTP, and TMP obtained instep S11 and constants KM and CM, by use of the following equation (5).

TM=KM×(TMP×2TP×LTP/1TP)+CM   (5)

The data representing the constants K2, KL, KM, C2, CL, and CM used inthe above steps S121 to S124 are stored in the non-volatile memory inthe central controller 250. These data are read out for use in thecalculations according to equations (3), (4), and (5).

As stated above, in step S12 the leading pulse widths and multi-pulsewidth in the write strategy used in recording are determined from theleading pulse widths and multi-pulse width in the recommended writestrategy parameters read from the optical disk. In other words, therecommended write strategy parameters are not used as is, but aremodified. The reason is as follows.

The recommended write strategy parameters, recommended asymmetry value,etc. are recorded in a predetermined area on the optical disk asdescribed above, but when the numerical aperture NA1 of the objectivelens 150 under the recording conditions when the recommended writestrategy parameters were recorded on the optical disk 160 differs fromthe numerical aperture NA2 of the objective lens 150 of the opticalrecording device 100 used in recording, if the power is determined byusing the recorded recommended write strategy parameters and asymmetryvalue, the amount of heat supplied to the optical disk 160 and itsdistribution differ due to the difference in the numerical aperture.Therefore, the size and shape of the pits formed corresponding to eachmark length are other than optimal, and jitter is worsened. The writestrategy is therefore modified or optimized to compensate for thedifference in recording conditions, particularly for the difference innumerical apertures.

The asymmetry value β2 used in recording is calculated in the above stepS13 based on the recommended asymmetry value β1 read from the opticaldisk. In other words, the asymmetry value β1 recorded on the opticaldisk is modified before being used. The reason for this is as follows.

The above difference in the numerical apertures causes a difference inthe detected asymmetry value. For example, when NA1<NA2, i.e., thenumerical aperture NA2 of the objective lens 150 of the opticalrecording device 100 used in recording is greater than the numericalaperture NA1 of the objective lens in the recording conditions underwhich the recommended asymmetry value was recorded on the optical disk160, the asymmetry value detected with an objective lens havingnumerical aperture NA2 has a larger value than the asymmetry valuedetected with an objective lens having numerical aperture NA1.Therefore, if recording is performed with an objective lens having anumerical aperture NA2 with a target value equal to the recommendedasymmetry value β1, the detected asymmetry value will have a highervalue than the actual value, due to the difference in the numericalaperture, and recording will be performed with an asymmetry valuesmaller than the recommended asymmetry value β1. Therefore, whenrecording is performed with an objective lens having a numericalaperture NA2, the target is preferably set to a higher value than therecommended asymmetry value β1.

Next, the above procedure will be described in detail. First, theoptimization of the write strategy will be described. It would bepreferable if the optimization correction could be performed by amathematical equation, but it was not clear what equation to use.

Therefore, the inventors conducted a variety of experiments to findconditions with minimum reproducing jitter, when the recordingconditions of the optical recording device used in recording differ fromthe recording conditions used in determining the recommended writestrategy parameters.

As a result, a linear relationship was found between the leading pulsewidth iTF (i=2 or L) that minimizes reproducing jitter (the pulse widththat minimizes reproducing jitter may also be referred to as the optimalpulse width or optimal value of the pulse width) and the recommendedpulse width parameter iTP (i=2 or L); from a regression analysisconducted on the data obtained in the experiment, it was found that thisrelationship could be approximated by lines represented by equations (3)and (4).

It was also found that the optimal value 1TF of the leading pulse widthin the write strategy for recording the shortest mark was equal to theoptimal value 2TF of the leading pulse width in the write strategy forrecording the second shortest mark, and that

the optimal value 3TF of the leading pulse width in the write strategyfor recording the third shortest mark was equal to the optimal value LTFof the leading pulse width in the write strategy for recording the marksfrom the fourth shortest mark to the longest mark.

It was further found that the optimal value TM of the multi-pulse widthwas linearly related to the value TMP×b 2TP×LTP/1TP calculated from therecommended pulse widths.

FIG. 6 shows circles representing the value of the leading pulse width2TF in the write strategy with minimum reproducing jitter, and a lineindicating the leading pulse width 2TF in the write strategy obtainedwhen K2=1 and C2=−0.02 in equation (3). As can be seen in the drawings,the deviation of the optimal values from the approximation line (theapproximation error) is small.

FIG. 7 shows circles representing the value of the leading pulse widthLTF in the write strategy with minimum reproducing jitter, and a lineindicating the leading pulse width LTF in the write strategy obtainedwhen KL=0.87 and CL=0.18 in equation (4). As can be seen in thedrawings, the deviation of the optimal values from the approximationline (the approximation error) is small.

FIG. 8 shows circles representing the value of the leading pulse width1TF in the write strategy with minimum reproducing jitter, and a lineindicating the leading pulse width 1TF in the write strategy obtainedwhen 1TF=2TF. It can be seen that 1TF and 2TF are almost the same.

FIG. 9 shows circles representing the value of the leading pulse width3TF in the write strategy with minimum reproducing jitter, and a lineindicating the leading pulse width 3TF in the write strategy obtainedwhen 3TF=LTF. It can be seen that 3TF and LTF are almost the same.

FIG. 10 shows circles representing the value of the multi-pulse width TMin the write strategy with minimum reproducing jitter, and a lineindicating the multi-pulse width TM in the write strategy obtained whenKM=0.18 and CM=0.435 in equation (5). As can be seen in the drawings,the deviation of the optimal values from the approximation line (theapproximation error) is small.

The conditions that were used in carrying out the experiments that gavethe results shown in FIGS. 6 to 10 were as the following. The numericalaperture NA1 of the objective lens in the recording conditions underwhich the recommended write strategy parameters were recorded on theoptical disk 160 was 0.60; the numerical aperture NA2 of the objectivelens 150 in the optical recording device 100 used in the experiments was0.64.

As described above, for a particular optical recording device, it wasfound that favorable results could be obtained when the constants areset as above.

Next, the modification of the asymmetry value will be described.

As noted above, the optimal asymmetry value is affected by the numericalaperture of the optical recording device used in recording, so when thenumerical aperture of the optical recording device differs from thenumerical aperture in the recording conditions under which therecommended write strategy was determined, the numerical aperture shouldbe taken into account in determining the asymmetry value to be used inrecording. In this embodiment, a correction determined from thedifference between the numerical apertures is added to the recommendedasymmetry value β1 to obtain an asymmetry value β2 to be used inrecording. Specifically, it was found appropriate to use the aboveequation (2).

β2=β1+E×(NA2−NA1)   (2)

This is the reason why equation (2) is used in step S13 in FIG. 4.

The triangles in FIG. 11 indicate the values of the asymmetry value β2that minimize the reproducing jitter in a certain optical recordingdevice 100 for a plurality of optical disks having mutually differingrecommended asymmetry value β1, and the straight line indicates theasymmetry value β2 obtained from equation (2) with E=1.0. As shown inFIG. 11, it was found that the asymmetry values (optimal asymmetryvalues) that minimize the reproducing jitter could be linearlyapproximated by use of equation (2).

As described above, it was found that for a certain optical recordingdevice, good results are obtained if the value of constant E is set asabove.

FIG. 12 shows reproducing jitter when three pulse patterns were used forrecording on each of nine types of optical disks A to I.

The X marks in FIG. 12 indicate the reproducing jitter when recordingwas performed using the recommended write strategy parameters recordedon each optical disk.

The triangular marks indicate the reproducing jitter when recording wasperformed using the optimized write strategy adjusted so as to obtainoptimal reproducing jitter for each optical disk.

The circles indicate the reproducing jitter when recording was performedusing the write strategy modified according to the above equations (3),(4), and (5).

The constants in equations (3), (4), and (5) in this case were set asfollows: K2=1, C2=−0.02, KL=0.87, CL=0.18, KM=0.18, CM=0.435, E=1.0.

In FIG. 12, better reproducing jitter could be obtained on all the diskswhen recording was performed using the modified recommended writestrategy parameters (as indicated by the circles) than when recordingwas performed using the recommended write strategy parameters recordedon each optical disk (as indicated by the X's). When recording wasperformed using the modified write strategy (as indicated by thecircles), it was possible to obtain nearly the same good reproducingjitter as when recording was performed using the optimal write strategy(as indicated by the triangles).

Thus according to the present embodiment, recording can be performedusing optimal write strategies and asymmetry values responsive to thecharacteristics of the optical system of the optical pickup of theoptical recording device.

For example, the optical system conditions such as the numericalaperture etc. used in determining the recommended parameters recorded onan optical recording medium generally differ from the optical conditionsof commercially available optical recording devices, but by takingaccount of the differences between the specifications of a commerciallyavailable optical recording device, particularly the specifications ofthe optical system of its optical pickup, and the specifications of theoptical system used in determining the recommended parameters, it ispossible to determine write strategy parameters and asymmetry valuessuitable for each optical recording device, and to perform recordingwith write strategies best suitable for each optical recording device.

The write strategies and asymmetry values suitable for each recordingdevice can be calculated easily if attention is paid to the differencesbetween optical recording devices, particularly differences in thecharacteristics of the optical systems of their optical pickups, moreparticularly optical system differences including the numericalapertures of their objective lenses, by experimentally determining theconstants (K2, KL, KM, C2, CL, CM, E) of the equations used to determinethe write strategies and asymmetry values, storing these constants inthe optical recording device, in non-volatile memory in the centralcontroller 250, for example, and reading out and using these storedconstants in recording.

The constants only need to be determined once for each type of opticalrecording device or set of specifications; the same constants can beapplied to other optical recording devices of the same type or with thesame specifications. Once constants have been determined for an opticalrecording device of a certain type or with certain specifications, otheroptical recording devices of the same type or with the samespecifications can be shipped with the constants that have beendetermined set therein.

When the type or specifications of the optical recording device 100 arechanged, the strategy conditions can be optimized easily by selecting ordetermining the constants (K2, KL, KM, C2, CL, CM, E) in equations (3),(4), and (5) again.

In the optical recording method according to the first embodiment,because the recommended write strategy parameters and the recommendedasymmetry value recorded on the optical disk 160 are calculated usingequations (3), (4), and (5), it is possible to support recording by anyrecording device on any recording medium without the need to store alarge amount of strategy information.

Recording can furthermore be performed better than when the recommendedwrite strategy parameters and recommended asymmetry value are usedwithout modification, and nearly as well as when the optimal recommendedwrite strategy parameters for each optical disk are used. Good recordingaccordingly can be performed on an optical disk for which the optimalwrite strategy information is not known beforehand.

In the above embodiment, the pulse width 1TF of the leading pulse F forrecording the shortest mark is set equal to the pulse width of theleading pulse F for recording the second shortest mark, and the pulsewidth 3TF of the leading pulse F for recording the third shortest markis set equal to the pulse width LTF of the leading pulse F for recordingthe fourth shortest mark to the longest mark, but the pulse widths ofthe leading pulse F may be given different values in each of thesecases.

That is, the pulse widths, such as in equations (3) and (4), can begeneralized as follows.

LTi=Ki×LTP+Ci

Second Embodiment

A recording method when the optical disk 160 is a dye-type recordingmedium is described in the first embodiment above. The following willdescribe a recording method when the optical disk 160 is a recordingmedium of the phase change type and, further, when recording is carriedout at the standard recording speed.

FIG. 13 shows an example of the basic structure of an optical recordingdevice 100 according to the second embodiment of the invention. Theoptical recording device 100 shown in FIG. 13 is generally the same asthe optical recording device in FIG. 1, except that it does not have theasymmetry detector 220 in FIG. 1 and instead has a modulation degreedetector 260. The central controller 250 receives a modulation degreevalue from the modulation degree detector 260 (instead of receiving anasymmetry value from the asymmetry detector 220), performs a calculationon the modulation degree instead of a calculation on an asymmetry value,and controls trial writing by using the modified write strategy andmodified modulation degree, instead of using a modified write strategyand an asymmetry value.

The modulation detector 260 detects the peak level B1 and the bottomlevel B2 of an input electrical signal. Using the equation (6) below, itcalculates a modulation degree value MOD from the detected peak level B1and bottom level B2.

MOD=(B1−B2)/B1   (6)

The peak level B1 and bottom level B2 occur in places where spaces ofmaximum length alternate with marks of maximum length; these valuesexpressed with the output level of the photodetector 180 when there isno incident light as the zero level.

FIGS. 14( a) and 14(b) show examples of modulation degrees of thereproduced signal detected in the modulation degree detector 260. FIG.14( a) shows an example with a comparatively small modulation degree.FIG. 14( b) shows an example with a larger modulation degree.

FIG. 15 shows examples of write strategies generated in the laserwaveform controller 240 in the optical recording device 100 shown inFIG. 13 when the optical disk 160 is a medium of the phase change type.FIG.(a) shows a channel clock with period T. FIG. 15( b) shows recordingdata consisting of marks and spaces. FIG. 15( c) shows the emittedoptical pulse pattern of a write strategy for recording the recordingdata in FIG. 15( b). In the emitted optical pulse pattern, the levelchanges between the recording power level, erasing power level, andreproducing power level, and the width of each pulse is defined as theperiod spent at the recording power level and reproducing power level.

The shortest mark has a length corresponding to 3T, while the longestmark has a length corresponding to 14T.

FIG. 15( b) and FIG. 15( c) assume a case in which the shortest mark isrecorded, then the fourth-shortest mark is recorded.

As shown at the left in FIG. 15( c), when the recorded data are theshortest mark, the write strategy consists of a leading pulse F havingpulse width 1TF, one subsequent multi-pulse M, and one subsequentcooling pulse C at the reproducing power level.

As shown at the right in FIG. 15( c), the write strategy for recordingthe fourth shortest mark consists of a leading pulse F having pulsewidth LTF, followed by four multi-pulses M, then a cooling pulse C atthe reproducing power level.

The write strategy for recording the n-th shortest mark (4<n<10, havinga length corresponding to ((n+2)T) consists of a leading pulse F havingpulse width LTF, followed by n multi-pulses M, then a cooling pulse C atthe reproducing power level.

The write strategy for recording the third-shortest mark (having alength corresponding to 5T) consists of a leading pulse F having pulsewidth LTF, followed by three multi-pulses M, then a cooling pulse C atthe reproducing level.

The write strategy for recording the longest mark (having a lengthcorresponding to 14T) consists of a leading pulse F having pulse widthLTF, followed by twelve multi-pulses M, then a cooling pulse C at thereproducing level.

As shown, the marks from the third shortest mark to the longest markhave the same leading pulse width LTF.

The write strategy recording the second shortest mark consists of aleading pulse F having pulse width 2TF, followed by two multi-pulses M,then a cooling pulse C at the reproducing level.

The width of the multi-pulse M is the same in all of the cases above.

The width of the cooling pulse C is the same in all of the cases above.

In a medium of phase change type, it is also a general practice tooptimize the recording power by performing trial writing beforerecording information.

First, trial writing is performed on the optical disk 160 by use of atest pattern comprising 3T-11T marks and spaces corresponding to randomrecording data, for example, under varied recording power; next, thearea on the optical disk 160 on which this test pattern has beenrecorded is reproduced, and the optimal recording power is obtained bycomparing the modulation degree detected by the modulation degreedetector 260 with a target value.

In general, the higher the recording power, the higher the modulationdegree, and the lower the recording power, the lower the modulationdegree.

The central controller 250 compares the detected modulation degreevalues corresponding to a plurality of mutually differing recordingpowers with the target value, and sets the recording power thatgenerated a detected value nearest to the target value as the optimalrecording power.

Alternatively, the trial writing on the optical disk 160 may beperformed at one recording power level, the data may be reproduced, themodulation degree may be detected from the reproduced data, the detecteddemodulation degree may be compared with the target demodulation degree,and the recording power may be increased or decreased responsive to thecomparison result to find the optimal value.

Within this basic information recording method, in the presentinvention, the power ratio in the write strategy for recording and therecording conditions such as the target value for adjusting the optimalpower are obtained by calculations based on the recommended writestrategy parameters and the recommended recording conditions recorded onthe optical disk 160 and the characteristics of the optical system ofthe optical pickup of the optical recording device used in recording;then the calculated power ratio and the target value for adjusting thepower are used in recording.

Next, the procedure for the optical recording method of this embodimentwill be described with reference to FIG. 16.

First, when the optical disk to be used in recording is inserted in theoptical recording device, in step S21, the recommended write strategyparameters and recommended recording conditions, i.e., the recommendedvalues iTP (i=1, 2, 3, L) of the leading pulse width in the writestrategy for recording each mark, the recommended value TMP1 of themulti-pulse width, the recommended power ratio value εP1 (the valuedefined by the erasing power/the recording power), and the recommendedrecording power value PW1 are read (step S21).

The recommended write strategy parameters include the recommended valueof the leading pulse width in the write strategy for recording eachmark. As the recommended values iTP of the leading pulse width, at leastthe recommended pulse width 1TP of the leading pulse F for recording theshortest mark is read.

Next, in step S22, the power ratio value εP1 to be used in recording isdetermined based on the recommended write strategy parameters that wereread in step S21 as described above (step S22).

ε1=KE1×(PW1εP1×TMP1)+CE1   (7)

Data representing constants KE1 and CE1 are stored in the non-volatilememory in the central controller 250, and these data are read and usedfor the calculation according to equation (7).

Next, in step S23, the modulation degree MOD1 to be used in recording isdetermined based on the recommended write strategy parameters that wereread in step S21 as described above (step S23).

MOD1=KMOD1×(TMP1×TCP1/1TP1)+CMOD1   (8)

Data representing constants KMOD1 and CMOD1 are stored in thenon-volatile memory in the central controller 250, and these data areread and used for the calculation in equation (8).

Next, when a recording command is received, trial writing on the opticalrecording medium is performed in step S24, using the power ratio andmodulation degree values obtained as above. The write strategydetermined in step S22 is set in the laser waveform controller 240,which in turn generates write strategies based on the test pattern toperform trial writing to the optical disk 160. At this time, themodulation degree MOD1 obtained as above is used as a target value. Thatis, the optimal recording power is determined by reproducing the area onthe optical disk 160 on which the test pattern has been recorded,comparing the modulation degree detected by the modulation degreedetector 220 with the modulation degree MOD1 calculated in step S23, andperforming control to make the two values match.

Then, after this trial writing has been performed and the power has beenadjusted, the adjusted recording power and the power ratio obtained instep S22 are used in step S25 to record data. That is, the power ratiodetermined in step S22 is set in the laser waveform controller 240,which in turn generates write strategies based on the recording data,and performs writing onto the optical disk 160 with the recording powerdetermined in step S24.

As described above, in step S22, the power ratio value to be used inrecording is determined based on the recommended pulse width value, therecommended recording power value, and the recommended power ratio valuein the write strategy that have been read from the optical disk. Inother words, the recommended power ratio value is not used as is, but ismodified. The reason is as follows.

The recommended power ratio value, etc. are recorded in a predeterminedareas on the optical disk as described above, but when the numericalaperture NA1 of the objective lens 150 in the recording conditions underwhich the recommended power ratio value was recorded on the optical disk160 differs from the numerical aperture NA2 of the objective lens 150 ofthe optical recording device 100 used in recording, if the power isdetermined by using the recorded recommended power ratio value, theamount of heat supplied to the optical disk 160 differs due to thedifference in the numerical aperture. Therefore, the size and shape ofthe pits formed corresponding to each mark length are other thanoptimal, and jitter is worsened. The power ratio is therefore modifiedor optimized to compensate for the difference in recording conditions,particularly for the difference in numerical apertures.

Next, the optimization of the power ratio will be described. It would bepreferable if the optimization correction could be performed by amathematical equation, but it was not clear what equation to use.

Therefore, the inventors conducted a variety of experiments to findconditions with minimum reproducing jitter, when the recordingconditions of the optical recording device used in recording differedfrom the recording conditions used in determining the recommended writestrategy parameters.

FIG. 17 shows circles representing the values of the power ratio εP1with minimum reproducing jitter in an optical recording device 100 for aplurality of optical disks with different values of the recommendedpower ratio εP1, and a line indicating the power ratio ε1 obtained whenKL1=0.029 and CE1=0.475 in equation (7). As shown in FIG. 17, it wasfound that the power ratio value (optimal power ratio value) withminimum reproducing jitter could be linearly approximated by usingequation (7).

As described above, it was found that for a certain optical recordingdevice, good results are obtained if the values of constants KE1 and CE1are set as above.

The constants are not limited to the above values, however; it isthought that satisfactory results are obtainable if KE1 is set to avalue near 0.03 and CE1 is set to a value near 0.48.

Next, the calculation of the modulation degree will be described.

The recommended value of the modulation degree is not recorded on theoptical disk 160, so it has to be estimated from the value of therecommended pulse width.

FIG. 18 shows circles representing the value of the modulation degreeMOD1 with minimum reproducing jitter in various optical disks on acertain optical recording disk 100, and a line indicating the value ofthe modulation degree MOD1 obtained when KMOD1=0.2 and CMOD1=0.59 inequation (8). As shown in FIG. 18, it was found that the modulationdegree (the optimal modulation degree value) with minimum reproducingjitter could be linearly approximated using equation (8).

As described above, it was found that for a certain optical recordingdevice, good results are obtained if the values of constants KMOD1 andCMOD1 are set as above.

The constants are not limited to the above values, however; it isthought that satisfactory results are obtainable if KMOD1 is set t6 avalue near 0.2 and CMOD1 is set to a value near 0.6.

FIG. 19 shows reproducing jitter when three power ratios were used forrecording on each of six types of optical disks A to F.

The X marks in FIG. 19 indicate the reproducing jitter when recordingwas performed using the recommended power ratio value recorded on eachoptical disk.

The triangular marks indicate the reproducing jitter when recording wasperformed using the optimized power ratio adjusted so as to obtainoptimal reproducing jitter for each optical disk.

The circles indicate the reproducing jitter when recording was performedusing the power ratio modified according to the above equation (7).

The constants in equation (7) in this case were set as follows:KE1=0.029, CE1=0.475.

In FIG. 19, better reproducing jitter could be obtained on all the diskswhen recording was performed using the modified recommended power ratiovalue (as indicated by the circles) than when recording was performedusing the recommended power ratio value recorded on each optical disk(as indicated by the X's). When recording was performed using themodified recommended power ratio (as indicated by the circles), it waspossible to obtain nearly the same good reproducing jitter as whenrecording was performed using the optimal power ratio (as indicated bythe triangles).

Thus according to the present embodiment, recording can be performedusing optimal power ratios and modulation degrees responsive to thecharacteristics of the optical system of the optical pickup of theoptical recording device.

For example, the optical system conditions such as the numericalaperture, wavelengths, etc. used in determining the recommendedparameters recorded on an optical recording medium generally differ fromthe optical conditions of commercially available optical recordingdevices, but by taking account of the differences between thespecifications of a commercially available optical recording device,particularly the specifications of the optical system of its opticalpickup, and the specifications of the optical system used in determiningthe recommended parameters, it is possible to determine the power ratioand modulation degree suitable for each optical recording device, and toperform recording under recording conditions suitable for each opticalrecording device.

The power ratio and modulation degree suitable for each recording devicecan be calculated easily if attention is paid to the differences betweenoptical recording devices, particularly differences in thecharacteristics of the optical systems of their optical pickups, moreparticularly optical system differences including the numericalapertures of their objective lenses, by experimentally determining theconstants (KE1, CE1, KMOD1, CMOD1) of the equations used to determinethe power ratio and modulation degree, storing these constants in theoptical recording device, in a non-volatile memory in the centralcontroller, for example, and reading out and using these storedconstants when recordings are made.

The constants only need to be determined once for each type of opticalrecording device or set of specifications; the same constants can beapplied to other optical recording devices of the same type or with thesame specifications. Once constants have been determined for an opticalrecording device of a certain type or with certain specifications, otheroptical recording devices of the same type or with the samespecifications can be shipped with the constants that have beendetermined set therein.

When the type or specifications of the optical recording device 100 arechanged, the recording conditions can be optimized easily by selectingor determining the constants (KE1, CE1, KMOD1, CMOD1) in equations (7)and (8) again.

In the optical recording method according to the second embodiment,because the power ratio and modulation degree used in recording arecalculated using the recommended pulse width values in the recommendedwrite strategy parameters recorded on the optical disk 160, therecommended power ratio value, the recommended recording power value,and equations (7) and (8), it is possible to support recording by anyrecording device on any recording medium without the need to store alarge amount of strategy information.

Recording can furthermore be performed better than when the recommendedpower ratio values are used without modification, and nearly as well aswhen the optimal recommended optimal power ratio value for each opticaldisk are used. Good recording accordingly can be performed on an opticaldisk for which the optimal power ratio is not known beforehand.

In equation (8), the recommended leading pulse width value of thestrategy pulse for recording the shortest mark is used, but therecommended leading pulse width value of the strategy pulse forrecording the second-shortest mark or the recommended leading pulsewidth value of the strategy pulse for recording the third-shortest markto the longest mark may be used instead.

Third Embodiment

The second embodiment above describes a recording method for use whenthe optical disk 160 is a recording medium of the phase change type andrecording is carried out at the standard recording speed. A recordingmethod for use when the optical disk 160 is a recording medium of thephase change type and recording is carried out at double speed will bedescribed below.

Double-speed recording uses the same write strategy as in recording atthe standard speed.

In this embodiment, the power ratio in the write strategy for recordingand the target value for adjusting the optimal power in the recordingconditions are determined by calculations based on the recommended writestrategy parameters and the recommended recording conditions that havebeen recorded on the optical disk 160 and the characteristics of theoptical system of the optical pickup of the optical recording device tobe used in recording, and recording is carried out by use of thedetermined power ratio and the target value for adjusting the power. Theoptical recording device used in this embodiment is the same as in FIG.13.

Next, the procedure followed in the optical recording method of thisembodiment will be described with reference to FIG. 16.

First, when the optical disk to be used in recording is inserted in theoptical recording device, in step S21, the recommended write strategyparameters for carrying out double-speed recording, i.e., therecommended values iTP2 (i=1, 2, 3, L) of the leading pulse width in thewrite strategy for recording each mark, the recommended power ratiovalue εP2 (the value defined as erasing power/recording power), and therecommended recording power PW2 are read from the optical recordingmedium (step S21).

The recommended write strategy parameters include the recommended valueof the leading pulse width in the write strategy for recording eachmark. As the recommended values iTP2 of the leading pulse width, atleast the recommended pulse width 1TP2 of the leading pulse F forrecording the shortest mark is read.

Next, in step S22, the power ratio value ε2 to be used in recording isdetermined based on the recommended write strategy parameters that wereread in step S22 as described above (step S22).

ε2=KE2×((PW2̂2)×εP2/1TP2)+CE2   (9)

Data representing constants KE2 and CE2 are stored in the non-volatilememory in the central controller 250; these are read and used for thecalculation according to equation (9).

Next, in step S23, the modulation degree MOD2 to be used in recording iscalculated, based on the recommended write strategy parameters that wereread in step S21 as described above according to the following equation(10) (step S23).

MOD2=KMOD2×(1TP2×PW2)̂2+KMOD3×(1TP×2PW2)+CMOD2   (10)

Data representing constants KMOD2, KMOD3, CMOD2 are stored in thenon-volatile memory in the central controller 250; these are read andused for the calculation according to equation (10).

Next, when a recording command is received, trial writing on the opticalrecording medium is performed in step S24, using the power ratio andmodulation degree values obtained as above. That is, the power ratiodetermined in step S22 is set in the laser waveform controller 240,which in turn generates write strategies based on a test pattern toperform trial writing to the optical disk 160. The modulation degreeMOD2 obtained as above is used as a target value. That is, the optimalrecording power is determined by reproducing the area on the opticaldisk 160 on which the test pattern has been recorded, comparing themodulation degree detected by the modulation degree detector 260 withthe modulation degree MOD2 calculated in step S23, and performingcontrol to make the two values match.

After this trial writing has been performed and the power has beenadjusted, the adjusted recording power and the power ratio obtained instep S22 are used in step S25 to record data. That is, the power ratiodetermined in step S22 is set in the laser waveform controller 240,which in turn, generates write strategies based on the recording data,and performs writing onto the optical disk 160 with the recording powerdetermined in step S24.

Next, the optimization of the power ratio will be described. It would bepreferable if the optimization correction could be performed by amathematical equation, but it was not clear what equation to use.

Therefore, the inventors conducted a variety of experiments to findconditions with minimum reproducing jitter, when the recordingconditions of the optical recording device used in recording differ fromthe recording conditions used in determining the recommended writestrategy parameters.

The circles in FIG. 20 indicate the values of the power ratio value ε2that minimize the reproducing jitter in a certain optical recordingdevice 100 for a plurality of optical disks having different recommendedpower ratio values δP2, and the straight line indicates the power ratiovalue ε2 obtained from equation (9) with KE2=0.0017, and CE2=0.125. Asshown in FIG. 20, it was found that the power ratio values (optimalpower ratio values) that minimize the reproducing jitter could belinearly approximated by use of equation (9).

As described above, it was found that for a certain optical recordingdevice, good results are obtained if the values of constants KE2 and CE2are set as above.

The constants are not limited to the above values however; it is thoughtthat satisfactory results are obtainable if KE2 is set to a value near0.002 and CE2 is set to a value near 0.13.

Next, the calculation of the modulation degree will be described.

Since the recommended value of the modulation degree is not recorded inthe optical disk 160, it is necessary to estimate its value from therecommended pulse width value.

The circles in FIG. 21 indicate the values of the modulation degree MOD2that minimize the reproducing jitter in a certain optical recordingdevice 100, and the curve indicates the modulation degree MOD2 obtainedfrom equation (10) with KMOD2=−0.01, KMOD3=0.18, and CMOD2=0.045. Asshown in FIG. 21, it was found that the modulation degree (optimalmodulation degree value) that minimizes the reproducing jitter could bequadratically approximated by use of equation (10).

As described above, it was found that for a certain optical recordingdevice, good results are obtained if the values of constants KMOD2,KMOD3, and CMOD2 are set as above.

The constants are not limited to the above values, however; it isthought that satisfactory results are obtainable if KMOD2 is set to avalue near −0.01, KMOD3 to a value near 0.2, and CMOD2 to a value near0.05.

FIG. 22 shows reproducing jitter when three power ratios were used forrecording on each of seven types of optical disks A to G.

The X marks in FIG. 22 indicate the reproducing jitter when recordingwas performed using the recommended power ratio values recorded on eachoptical disk.

The triangular marks indicate the reproducing jitter when recording wasperformed using the optimized power ratios adjusted so as to obtainoptimal reproducing jitter for each optical disk.

The circles indicate the reproducing jitter when recording was performedusing the power ratio modified according to the above equation (9).

The constants in equation (9) in this case were set as follows:KE2=0.0017, CE2=0.125.

In FIG. 22, better reproducing jitter could be obtained on all the diskswhen recording was performed using the modified recommended power ratiovalues (as indicated by the circles) than when recording was performedusing the recommended power ratio values recorded on each optical disk(as indicated by the X's). When recording was performed using themodified power ratio values (as indicated by the circles), it waspossible to obtain nearly the same good reproducing jitter as whenrecording was performed using the optimal power ratios (as indicated bythe triangles).

Thus according to the present embodiment, recording can be performedusing optimal power ratio and modulation degree values responsive to thecharacteristics of the optical system of the optical pickup of theoptical recording device.

For example, the optical system conditions such as the numericalaperture etc. used in determining the recommended parameters recorded onan optical recording medium generally differ from the optical conditionsof commercially available optical recording devices, but by takingaccount of the differences between the specifications of a commerciallyavailable optical recording device, particularly the specifications ofthe optical system of its optical pickup, and the specifications of theoptical system used in determining the recommended parameters, it ispossible to determine power ratios and modulation degrees suitable foreach optical recording device, and to perform recording with writestrategies best suitable for each optical recording device.

The power ratios and modulation degrees suitable for each recordingdevice can be calculated easily if attention is paid to the differencesbetween optical recording devices, particularly differences in thecharacteristics of the optical systems of their optical pickups, moreparticularly optical system differences including the numericalapertures of their objective lenses, by experimentally determining theconstants (KE2, CE2, KMOD2, KMOD3, CMOD2) of the equations used todetermine the power ratios and modulation degrees, storing theseconstants in the optical recording device, in a non-volatile memory inthe central controller, for example, and reading out and using thesestored constants when recordings are made.

The constants only need to be determined once for each type of opticalrecording device or set of specifications; the same constants can beapplied to other optical recording devices of the same type or with thesame specifications. Once constants have been determined for an opticalrecording device of a certain type or with certain specifications, otheroptical recording devices of the same type or with the samespecifications can be shipped with the constants that have beendetermined set therein.

When the specifications of the optical recording device 100 are changed,the recording conditions can be optimized easily by selecting ordetermining the constants (KE2, CE2, KMOD2, KMOD3, CMOD2) in equations(9) and (10) again.

In the optical recording method according to the third embodiment,because the power ratio and modulation degree values used in recordingare calculated according to equations (9) and (10), using therecommended power ratio value in the recommended write strategyparameters recorded on the optical disk 160, recordings can be made byany recording device on any recording medium without the need to store alarge amount of strategy information.

Recording can furthermore be performed better than when the recommendedwrite strategy parameters and recommended asymmetry value are usedwithout modification, and nearly as well as when the optimal recommendedoptimal write strategy parameters for each optical disk are used. Goodrecording accordingly can be performed on an optical disk for which theoptimal write strategy information is not known beforehand.

In equations (9) and (10), the recommended leading pulse value of thestrategy pulse for recording the shortest mark is used, but therecommended leading pulse width in the write strategy for recording thesecond-shortest mark or the recommended leading pulse width in the writestrategy for recording a mark from the third-shortest mark to thelongest mark may be used instead.

Although the pulse widths are not adjusted (the recommended pulse widthvalues are not modified) in the second and third embodiments above,these embodiments may be adapted to adjust the pulse widths.

1. An optical recording method comprising the steps of: reading arecommended power ratio and a recommended recording power value of awrite strategy from a phase change optical recording medium on which therecommended power ratio and the recommended recording power value arerecorded as recommended write strategy parameters; determining a powerratio and a modulation degree for use in recording, based on therecommended power ratio and the recommended recording power value in therecommended write strategy parameters thus read, and characteristics ofan optical system of an optical pickup of an optical recording deviceused for recording; and writing to the optical recording medium by useof the optical recording device, using the power ratio and themodulation degree thus determined.
 2. The optical recording method inclaim 1, wherein: a recommended pulse width is also recorded on thephase change recording medium as a write strategy parameter; the step ofreading further comprises reading the recommended pulse width in thewrite strategy; and the step of determining determines the power ratioand modulation degree used for recording from the recommended pulsewidth in the write strategy, as well as from the recommended power ratioand recommended recording power value in said write strategy and thecharacteristics of the optical system of the optical pickup of theoptical recording device used for recording.
 3. The optical recordingmethod in claim 1, wherein: said step of determining is carried out bycomputations using formulas predetermined for the optical recordingdevice used in recording; target values of the power ratio andmodulation degree that minimize reproducing jitter are determinedexperimentally, formulas are generated such that the experimentallydetermined power ratio and modulation degree values are results ofcalculations or values approximating the results of the calculations,and the generated formulas are used in said step of determining.
 4. Theoptical recording method of claim 3, wherein: said step of reading alsoreads a multi-pulse width in the recommended write strategy parameters;and the formula for determining the power ratio for recording at a 1×recording speed is expressed asε1=KE1×(PW1×εP1×TMP1)+CE1 (where ε1 is the value of the power ratio usedfor recording, PW1 is the recommended recording power value, εP1 is therecommended power ratio, TMP1 is the multi-pulse width in therecommended write strategy parameters, and KE1 and CE1 are constants fordetermining the power ratio).
 5. The optical recording method of claim3, wherein: said step of reading also reads a leading pulse width in therecommended write strategy for recording the shortest mark, amulti-pulse width, and a cooling pulse width in the recommended writestrategy parameters; and the formula for determining the modulationdegree parameter for recording at a 1× recording speed is expressed asMOD1=KMOD1×(TMP1×TCP1/1TP1)+CMOD1 (where MOD1 is the value of themodulation degree used for recording, TMP1 is the multi-pulse width inthe recommended write strategy parameters, TCP1 is the cooling pulsewidth in the recommended write strategy parameters, 1TP1 is the leadingpulse width in the recommended write strategy parameters for recordingthe shortest mark, and KMOD1 and CMOD1 are constants for determining themodulation degree parameter).
 6. The optical recording method of claim3, wherein: said step of reading also reads a leading pulse width in therecommended write strategy parameters for recording the shortest mark;and the formula for determining the power ratio for recording at a 2×recording speed is expressed asε2=KE2×(PW2̂2×εP2/1TP2)+CE2 (where ε2 is the value of the power ratioused for recording, PW2 is the recommended recording power value, εP2 isthe recommended power ratio, 1TP2 is the leading pulse width in therecommended write strategy parameters for recording the shortest mark,and KE2 and CE2 are constants for determining the power ratio).
 7. Theoptical recording method of claim 3, wherein: said step of reading alsoreads a leading pulse width in the recommended write strategy forrecording the shortest mark, a cooling pulse width, and a multi-pulsewidth in said recommended write strategy parameters; and the formula fordetermining the modulation degree parameter for recording at a 2×recording speed is expressed asMOD2=KMOD2×(1TP2×PW2)̂2+KMOD3×(1TP2×PW2)+CMOD2 (where MOD2 is the valueof the modulation degree used in recording, 1TP2 is the leading pulsewidth in the recommended write strategy parameters for recording theshortest mark, PW2 is the recommended recording power value, and KMOD2,KMOD3, and CMOD2 are constants for determining the modulation degreeparameter).
 8. An optical recording device with an optical pickup havingan optical system for recording and reproducing, comprising: a readingmeans for reading a recommended power ratio and a recommended recordingpower value in a write strategy from a phase change optical recordingmedium on which the recommended power ratio and the recording powervalue are recorded as recommended write strategy parameters; adetermining means for determining a power ratio and a modulation degreefor use in recording, based on the recommended power ratio and therecommended recording power value in the recommended write strategyparameters thus read and characteristics of the optical system of theoptical pickup; and a writing means for writing to the optical recordingmedium, using the power ratio and the modulation degree thus determined.9. The optical recording device in claim 8, wherein: a recommended pulsewidth in the write strategy is also recorded on said phase changeoptical recording medium; the reading means also reads the recommendedpulse width in the write strategy; and the determining means determinesthe power ratio and modulation degree parameter used for recording fromthe recommended pulse width in the write strategy, as well as from therecommended power ratio and the recommended recording power value in therecommended write strategy parameters and the characteristics of theoptical system of the optical pickup used for recording by the opticalrecording device.